Manipulating digital photos with conventional photo editing software is generally very easy. While editing photos may be quite permissible in a private setting, in other procedures, such as lawsuits where the photo is to be used as evidence, it must be possible to prevent subsequent manipulation altogether. However, photos have little probative value because they are so easy to alter.
A method is known from U.S. Pat. No. 7,616,237 B2 that can be used to demonstrate whether a photo has been created with a given digital camera. For this, several photos are taken with the camera. A reference sample is calculated from these several photos representing an approximation of a signal noise in the photos. A noise pattern is determined for a test image. The noise pattern is compared with the reference sample and on this basis it is determined whether the test image was created with the digital camera. In this way, the method is similar to the ballistics testing of a projectile to determine whether the projectile was fired from a given gun.